Alkalinity questions

[onux20]

I have been dosing 2-part for about two months now I guess. I 'understand' the basic relationship between Ca, Mg, and Alk. I rarely test the Ca or Mg but regularly test Alk. Typically I dose anbd test in the AM well before the lights come on. I add both parts within 1 min of each other. What I consider slowly, 4 -5 pours to add 10ml. My goal is to keep Alk around ten. So far I have been able to get it there for one day but not maintain it. Which leads to my question,

 

How much should I expect Alk to decline from day to day?

Is going from a dKh of 10 to 8 okay in one day? Expected?

Does it decline as some function of how much Ca is being consumed daily?

Is it a moving target that I will always be chasing?

I am I doing something horribly wrong?

 

Okay that was more than one question but...

My thoughts are its either a function of Ca usage or depletion of Mg. I don't trust my Mg test kit, it always reads high. I'm trying to decide if it is worth buying another to test Mg regularly. I would hope dKh would not fluctuate so much from day to day. I expected to only dose 2 Part a couple times a week once I got Alk where I wanted it.

 

All other params are within the 'GARP---Generally Accepted Reefing Parameters'

 

 

Coral Inhabitants:

Random Acro frag (Just started turning green with reddish polyps)

Pink Millie (hints of blue. Thanks Steve Outlaw!)

Pink BN (great Polyp ext)

Chalice Frag

Idaho Grape Monti (Constantly sliming...constantly being moved)

Orange Monti ( doing okay, growth slowed)

Orange Plate (fading)

Flower pot (doing fine...I guess)

Torch Coral (ditto)

Unhappy red digi (partial polyp ext)

Unhappy green digi (no polyp ext)

Unhappy leather

Shrooms, Zoas, Feather Duster

Overall the coral seem okay. The Digis and plate are giving me troubles. But its just those and not the others.

 

Fish

Pygmy Angel

Clown (not sure of type)

Bi Color Blenny

Chromis

Cleaner Shrimp

Emerald Crab

Clean-up Crew

 

 

I have said enough I hope...

Advice is appreacited.

Ron

[ReeferMan]

Dosing pump would help keep it constant

[ctenophore]

How much should I expect Alk to decline from day to day?

This directly depends on how many alk consumers you have. Examples: all stony corals, coralline algae, deep sandbed.

 

Is going from a dKh of 10 to 8 okay in one day? Expected?

Not okay. Are you sure your alk kit is reading correctly? My old tank had about 100 lbs of live sps, and the alk would only fall 1 to 1.5 dkh/day if my calcium reactor ran out of CO2. For yours to fall 2 dkh is unexpected.

 

Does it decline as some function of how much Ca is being consumed daily?

Yes, Ca and alk are consumed proportionally.

 

Is it a moving target that I will always be chasing?

Yes, unless you devise a better system for adding the two-part. Have you looked into the "Drew's Doser" dosing pumps from bulkreefsupply.com? I have used these with good success. If they are out you can also buy them from APT Instruments.

 

I am I doing something horribly wrong?

It sounds like you're doing something wrong, but maybe it's just the kit.

 

FWIW, I use the Salifert alk kit since it comes with a reference solution for calibration, and the Tropic Marin Ca/Mg combo kit.

 

Hope this helps.

Justin

[Brian Ward]

Your aquarium 'consumes' alkalinity in the process of calcification. All the corals (LPS and SPS) and coraline algae contribute to the depletion of alkalinity. You do need to test for calcium to see how much of that is being used daily as well. You should be doing at least daily, and ideally multiple times per day doses to maintain the alkalinity and calcium as it is depleted. Problem #1: You should not be dosing alk and calcium that close together. You need to give whichever part you dose first about 5-10 mins to dissipate into the water and stabilize before you add the other part. Otherwise you will cause the alk and calcium to combine and precipitate out. Problem #2: If you know that the amount your dosing still causes your alk to decline by 2dKH daily, then you should up the amount you're dosing. Hopefully the alk and calcium are declining equally, but that's not guaranteed. This is why the dosing pump would be helpful - it will contstantly add chemical to the water throughout the day to maintain the chemistry.

[SkiCurtis]

That why I love WAMAS members for there helpful and educational expertise in subjects that are very important. thanks for the info. I always monitor my levels and also dose. the reef calculator @ bulk reef supply has gotten me to a level where I know how much to dose each day. I'm up to 8 oz a day. Man do I need a calcium reactor.

Curtis

[bshriver]

On magnesium:

1) Low magnesium will make it harder to maintain alk and ca as it is high magnesium that allows ca and alk to exist in a supersaturated state in seawater. I can link you to a Randy Holmes Farley article on RC if you want since the details of the chemistry is not comitted to memory

 

2) My experience with magnesium test kits has been that most of them read very high. I believe this is because CA looks very similar to Mag chemically and the test kits report some of the CA as Mag - just a guess. The SeaChem kit has an extra precipitation step that I presume is to precipitate out the CA. The SeaChem kit also provides a reference solution to validate the kit's measurements. I use that solution to validate other kit's and they tend to read high when CA levels are near or above 400. The Elos kit is the only one other than SeaChem that I have had any luck with. The Elos kit is a quicker test than the SeaChem one.

 

Good luck!

[onux20]

I just ran a round of tests. Here are my values all off Tropic Marin Kits

 

Ca 420

Mg 1440

Alk 8dKh

Temp 80

Sg 1.026

 

So it doesnt look like my Mg is low. Wont draw any conclusions from just one data point. I will continue to test and record values.

 

Thanks to all for the advice.

 

Ron

[CHUBAKAH]

Just out of curiosity, what type of salt mix do you use Ron?

[onux20]

Just out of curiosity, what type of salt mix do you use Ron?

Reef crystals